HR: 1330h
AN: H52A-1157    [PDF]
TI: One-Dimensional Sediment Transport and Turbulence
AU: * Dodd, A M
EM: amdodd@cc.usu.edu
AF: Utah State University Civil and Environmental Engineering Department, 4110 Old Main Hill, Logan, UT 84322 United States
AU: Cashman, E M
EM: emc7001@humboldt.edu
AF: Humboldt State University Environmental Engineering Department, 1 Harpst Street, Arcata, CA 95521 United States
AU: Hardy, T B
EM: hardy@aaron.cee.usu.edu
AF: Utah State University Civil and Environmental Engineering Department, 4110 Old Main Hill, Logan, UT 84322 United States
AB: The goal of this research is to incorporate the influence of turbulence into an existing one-dimensional sediment transport model. Typically sediment transport models evaluate transport under mean flow conditions. Here, a new model formulation that accounts for turbulence will be developed. The results from an experimental flume study will be used to evaluate and compare the results of the traditional model and the model that incorporates turbulence. The flume experiments are being conducted in a research quality sediment transport flume, capable of simulation of open channel flows and sediment, at Humboldt State University. The one-dimensional average flow method utilizes the average longitudinal flow velocity to determine the sediment transport threshold condition and overall transport. The turbulent method utilizes current research results regarding eddy structure and turbulent velocity fluctuations. The eddy structure, which is cyclic in nature, contains four events (sweeps, ejections and inward and outward interactions) defined by the longitudinal and vertical velocity fluctuations. Recent research indicates that the longitudinal normal stress is the most dominant in particle entrainment. Thus, if the events that make up an eddy are considered as separate cells, an initial eddy structure is assumed, an estimate of the turbulent longitudinal velocity determined, and the rolling eddies are followed through the model, it may be possible to simulate the cyclic process. The fluctuating longitudinal velocity within each cell is determined at random from a Gaussian distribution. Given the time-averaged velocity from the flow model, the instantaneous longitudinal velocity is estimated as a sum of this average and the fluctuating component. If this velocity meets a threshold criterion then sediment transport within the cell will occur. The amount moved will be determined using an empirical sediment relation and will depend on the time associated with the fluctuation and the size of the cell associated with the turbulent event. A one-dimensional model that incorporates turbulence in this way may be useful in understanding the role of turbulence on sediment transport.
DE: 1815 Erosion and sedimentation
DE: 3210 Modeling
SC: Hydrology [H]
MN: 2003 Fall Meeting